CP violation Asymmetry

after discovery of violation of parity in 1956-57, believed combined symmetry of parity (p) , simultaneous charge conjugation (c), called cp, preserved. example, cp transforms left-handed neutrino right-handed antineutrino. in 1964, however, james cronin , val fitch provided clear evidence cp symmetry violated in experiment neutral kaons.

cp violation 1 of necessary conditions generation of baryon asymmetry in universe.

combining cp symmetry simultaneous time reversal (t) produces combined symmetry called cpt symmetry. cpt symmetry must preserved in lorentz invariant local quantum field theory hermitian hamiltonian. of 2006, no violations of cpt symmetry have been observed.